/Engine/Source/Runtime/Engine/Classes/Curves/SimpleCurve.h
Finds the key at InTime, and updates its value. If it can't find the key within the KeyTimeTolerance, it adds one at that time
virtual [FKeyHandle](API\Runtime\Engine\Curves\FKeyHandle) UpdateOrAddKey ( float InTime, float InValue, const bool bUnwindRotation, float KeyTimeTolerance )